Driving in "B" all the time

[psyflyjohn]

I've been having fun fooling with the "gear" settings since I got the Miev this spring. I've followed the manual's recommendations for different driving conditions. Recently, I decided to just put the selector in "B", and leave it there.
I like the braking effect it has in stop and go traffic, feeling that I am getting maximum regeneration when slowing down. Even at expressway speed, the "B" setting seems to give me more positive control, with little or no penalty in charge loss.

Any others out there doing the same thing? Is there an unknown penalty for doing this?

 

[joev]

I use "B' mode all the time! I like it also to control the rate of "braking" to slow you down.
I only noticed a slight decrease in kw/mile, that is a good thing.

 

[fjpod]

My concern with driving in B all the time is if you overuse the braking, and then you have to speed up again, you are wasting energy. The goal is to drive as if you have no brakes. Using a lot of regen means you are accelerating too much in the first place.

Also B gives you "full power" on the throttle so you will be inclined to accelerate more.

 

[peterdambier]

Sometimes long lonely streets, I use "C" but that is very rarely. I am in "B" most of the time. It gives me time when suddenly breaking in traffic jams. It is either up the hill or down the hill here in the mountains. So "B" is a lot more comfortable than breaking all the time.

Yes there is a penalty. I am living 1/3 down the other side of the hill. Going up with full batteries and coming down the other side again, half way down regen stops and I have to use the breakes. At that moment there is no diff between "C" or "B". With "C" or "D" I would not notice but with "B" it feels like suddenly the breakes would fail.

There is another penaly, take care of the breaks. They might get rusty.

 

[NeilBlanchard]

Free wheel coasting when you need to carry speed is better - if you put it in neutral, just coast using the kinetic energy of the car directly without any conversion losses.

When you need to slow down, use D or B for increasing amounts of regen. This is better than using the friction brakes (obviously) but there are a certain amount of losses (generation, charger, and the battery being the main ones), so it is not as efficient as coasting.

If you never had to use any regen or brakes, then you have used *just* enough accelerator. That is the ideal, but is rarely achievable - minimal regen and a wee bit of brakes are usually needed.

 

[danpatgal]

I also started my iMiev driving almost exclusively in B. Depending on how far I pressed the pedal I could accelerate or decelerate as traffic or my hypermiling eco-conscious willed me to drive. But, I found that I got a little bit too much regen if I didn't have a lot of foot discipline. And, I liked that in 'E' acceleration was dampened. If I ever crest a big hill, it's very easy to drop down to B. And, if I feel like letting the car ride a little looser, like on the highway, I can put it in 'D' without much trouble either. So, now I almost always just start in 'E' and then go from there ...

 

[tonymil]

I've always been a leadfoot so if I drive in B or D mode I end up losing range. I drive in Eco mode instead. I'll pop it into B mode before hitting the brakes and only brake when/if I have to.

Be careful about coasting in neutral, it's illegal in most states, although I don't know how a cop would know that you're doing it. But also, if you're presented with an emergency, you may forget your in neutral and press the accelerator expecting something to happen and when it doesn't.... which is maybe why it's illegal.

 

[fjpod]

Free wheel coasting when you need to carry speed is better - if you put it in neutral, just coast using the kinetic energy of the car directly without any conversion losses.

When you need to slow down, use D or B for increasing amounts of regen. This is better than using the friction brakes (obviously) but there are a certain amount of losses (generation, charger, and the battery being the main ones), so it is not as efficient as coasting.

If you never had to use any regen or brakes, then you have used *just* enough accelerator. That is the ideal, but is rarely achievable - minimal regen and a wee bit of brakes are usually needed.

+1

 

[fjpod]

I also started my iMiev driving almost exclusively in B. Depending on how far I pressed the pedal I could accelerate or decelerate as traffic or my hypermiling eco-conscious willed me to drive. But, I found that I got a little bit too much regen if I didn't have a lot of foot discipline. And, I liked that in 'E' acceleration was dampened. If I ever crest a big hill, it's very easy to drop down to B. And, if I feel like letting the car ride a little looser, like on the highway, I can put it in 'D' without much trouble either. So, now I almost always just start in 'E' and then go from there ...

I do the same. I agree that using B all the time requires too much "foot discipline" to be efficient. It's good for rolling down a very steep hill where you have to stop at the bottom...OTW it is best to never "need" regen.

Someone else made reference to using B instead of the brakes...but remember, the brakes are regenerative also (unless you do panic braking), so it doesn't matter if you use B or the stop pedal as long as you do it gradually. One just has to look at the Eco indicator in the charge area as evidence. Be careful of using too much B braking as you have no rear tail light indicating that you are slowing.

 

[MLucas]

After trying out D and E when I first bought the car, I'm now in B all the time. It just takes some practice to drive it as efficiently as possible. I can get just as good numbers in B as in E. Accelerating, yes its easy to push the amp meter beyond the green zone but with some discipline its also easy to keep it under the first peg. I find this a nice safety feature, because if you ever needed full power - you got it and I've had to use it while accelerating onto the highway. Starting out nice and easy and then I notice a truck comes out of nowhere with something to prove.

With this same discipline, I keep it in the black zone between the regen and econ zones when I'm going down hills or coasting. For stopping, I simply ease off the amp pedal (why waste that kinetic energy and eat my brakes?) and bring up the regen and apply the brakes within the last 10ft. I see this as no different than a manual transmission using the gears to slow the car down instead of the brakes. So we aren't the only ones coasting to a stop without brake lights.

I agree with tonymil, if you are a leadfoot then E makes it easy to keep it green.
I found E really helpful when I first bought the car to learn how to drive it as efficiently as possible. It definitely has its purpose.
Whereas D I think is for those that don't get electric cars and just want to see what it can do.

 

[JoeS]

Just a point of clarification: flooring it in Eco still provides full power.

Eco reduces the amount of power delivered for a given pedal position compared to the other two modes, provides more regen than D but less than B, and also adds a mechanical resistance to the pedal. Cute feature which I use when driving around town. Since I personally find it difficult to maintain the zero regen position (midway between green and blue), when I am hypermiling (to maximize my range) then a lot of my driving alternates between D and N, acknowledging all the caveats.

Back on topic, I find B very useful for performance driving on twisty mountain roads, but otherwise I find it all-to-easy to unnecessarily induce (wasteful) regen. On the other hand, I am constantly shifting amongst N-D-E-B when slowing down and usually only touch the brake pedal in order to come to a full stop (yes, yes, I'm mindful of those behind me regarding brake lights).

 

[Don]

I also use B exclusively - Nearly 6,000 miles now and probably less than 10 or 15 of those miles were in any other mode

First, there is no 'freewheel' choice, since the transmission always has the motor directly connected to the wheels, unlike an auto trans car, so all shifting into Neutral gets you is that you've disconnected the motor from power and also from regen - You can do the same with the foot pedal, though it does require a steady foot - Actually, if done correctly by feathering in only an amp or two, the car truly coasts much the same as a manual transmission does when you push in the clutch. No matter what mode you use, you are either accelerating, coasting or braking and you can do all of those so easily with the B mode, plus it gives you the most energy recovery when you need to slow down. You could of course coast a quarter of a mile up to every stop sign in D or Eco, but who actually drives this way? Most drivers use the brakes to slow . . . . I use regen in B mode and don't touch the brakes until the speed is down to 10 or 12 mph

Anyone who complains that B is giving them too much regen is just not modulating the pedal correctly - You can get as much or as little regen as you need just by modulating the pedal correctly - You can go up a hill and down the other side at exactly the same speed, once you get a feel for what you need to do with the pedal

If you came to EVing from driving manual transmission cars, exclusive use the B mode gives you much the same feel. With a manual transmission car, the motor and the wheels are directly connected and with the go pedal you are either accelerating, 'coasting' (neither accelerating nor decelerating . . . . 'neutral pedal') or you are decelerating with the engine braking the car - It all works much the same driving the iMiEV in B mode. It was a perfectly natural transition for me

Observing many people who have little to no experience with manual transmission cars though, it became obvious that many of them actually drive most every mile by pressing lightly on the pedal and then releasing it to 'coast' (which an automatic transmission allows you to do) and then pressing the pedal again when they notice the speed has dropped off a bit - The pedal is never held steady, but is slowly pumped up and down, all the while maintaining a fairly constant speed. Watching hundreds of drivers do this over the years it's obvious (at least to me) that they don't even realize what they are doing. If you're accustomed to driving this way, then the 'D' mode in the iMiEV was designed specifically for you, as it has the least regen 'penalty' for you when you inadvertently release the pedal

Since my 45 years of all manual transmission experience has taught me to maintain a very even pedal and only release it when I actually need to slow down, the B mode is what gives me the most realistic comparison to driving the manual transmission cars I love so much . . . . plus, if done correctly, it's also the most 'fuel efficient' way to drive an EV

Don

 

[MLucas]

Very nice explanation, Don. B does feel closest to a manual transmission when using the gears to slow down instead of the brakes.

 

[JoeS]

OTOH, never having owned a automobile with an automatic transmission, I presently own two vehicles that are perhaps relevent to this discussion:

1. My 1967 Saab 96V4 (owned since new - it was my 1967 Christmas present to myself) has a wonderful "freewheel" feature, which disengages the transmission when you let go of the gas pedal. Think of it as a uni-directional drive. Basically, the car is coasting in neutral whenever the gas pedal is released. My driving style with this particular car is to accelerate and let-go the gas pedal. Amazing how much time is spent 'coasting', and 45 years of doing this is a hard habit to break. :roll:
2. I've installed something called MIMA into my 2002 Honda Insight hybrid. What this gives me is a little joystick that gives me fully-independent fingertip control over the electric motor, a feature I would love to have on my iMiEV. My claim to fame is a lifetime average mileage presently down to 77.3 mpg for over 85,000miles. Independently of this feature, with this Insight, my driving style is also "Pulse-and-Glide", where the gliding is indeed shifting into Neutral, often with the car in FAS (Forced Auto Stop) - with fuel injectors cutoff. Very safe in this particular car because of its safety features which automatically turn the engine back on.

Due to the excellent aerodynamics of both cars, letting the car coast results in a barely-perceptible slowing of the car when surrounded by traffic. Since I live in a hilly area, I perhaps derive even more benefit from these techniques than if I lived in flatter country.

Finally, the problem I have with the iMiEV B mode in normal highway driving is that holding the go-pedal steady in the zero-energy spot requires, in my opinion, way too much concentration. It's far easier to just toss the car into N and simulate "freewheel". Any time you have forward motion with the car in "Neutral" you are neither consuming electrical energy nor robbing the car of kinetic energy.

Don and I have agreed to disagree on this topic in the past - I think it's just a matter of different strokes for different folks

 

[BillThompsonMIEV]

I guess I'm in the school of always haven driven automatic transmisson cars. To me, the E mode works fine. It gives me regen when I slow down, and my average RR after a full charge is about 90 miles. I have tried B mode, but to me it seems to slow down too much when I take my foot off the go pedal. Well, we have three choices and all is well.

 

[MLucas]

This whole discussion has gotten me to think about Regen and driving modes. I've noticed that sometimes my foot is still on the amp pedal and applying slight pressure but my Amp meter is telling me that I'm in Regen mode.

Tell me if I'm wrong or not.

Are we not controlling Regen by using the amp pedal? It feels to me that the first zone on the amp pedal is actually the Regen control zone. As I apply lighter and lighter pressure, I go deeper into the Regen mode until I no longer apply any pressure and I'm at maximum Regen. If I apply pressure again, the Regen lightens up and I start moving into the green zone. It seems the computer understands when I'm stopped and applies power and when I'm already under power and changes the behaviour of the amp pedal to a Regen control pedal? Seems like similiar behaviour in the brake but without using the brake. I like seeing how far I can go without touching the brakes to stop and playing with the amp pedal allows me to do this. I look ahead and see a light, stop sign, whatever and ease off the amp pedal and get the Regen in the upper part of its range to begin to slow down, then I gauge my distance and apply more or less pressure to reach my stop point. Then at the last few feet, I ease on the brake pedal and stop with finesse. To me, this seems like I'm controlling the Regen. Thoughts?

 

[tonymil]

This whole discussion has gotten me to think about Regen and driving modes. I've noticed that sometimes my foot is still on the amp pedal and applying slight pressure but my Amp meter is telling me that I'm in Regen mode.

Tell me if I'm wrong or not.

I think you have to look at whether you are going uphill, downhill or are on level terrain. If you're putting just enough pressure to maintain speed and then go from level terrain to downhill, you naturally ease up on the accelerator to avoid accelerating, but that may move the needle to regen. You still have your foot resting on the pedal but you're not actually drawing energy from the battery. The only way to be in regen on flat terrain is if you're decelerating.

 

[Don]

This whole discussion has gotten me to think about Regen and driving modes. I've noticed that sometimes my foot is still on the amp pedal and applying slight pressure but my Amp meter is telling me that I'm in Regen mode.

Tell me if I'm wrong or not.

If you're using the B mode, you're definitely correct

To go up a hill (such as a freeway overpass) at a steady 30 mph, you press into the green zone on the amp gauge to whatever amount is required to maintain the 30 mph - Trying to accelerate will require more pedal of course. As you near the top, you need less and less pedal and then when you begin going down the other side, less pedal yet. You cannot let off the pedal completely or the B mode regen will begin to slow you down, so you do exactly what you described . . . . you modulate the pedal for the proper amount of regen needed to brake the car only enough so you maintain your 30 mph exactly - You *will* be seeing the needle over in the blue, because regen is what is keeping the car from gaining speed on the downhill

This is what I was trying to describe earlier - Some here say that B gives too much regen and they are slowing when they don't intend to, but this is only because they're not modulating the pedal properly. Once you get the hang of this, the car is an absolute blast to drive because you can literally go anywhere you want with next to no friction braking needed - You maintain exactly the speed you desire both uphill and downhill just by modulating the 'go' pedal

I suppose it's not the perfect way to drive for everyone because it does require the driver to be concentrating on what he's doing 100% of the time, but this is the way I've always driven every car I've ever had, so it works perfectly for me

Joe - My very first car was a 1953 Plymouth with a flathead six and 'three in the tree' with an electric overdrive. When in the overdrive mode, it behaved exactly as your Saab does - Complete freewheel when you released the pedal . . . . or when you came to any hill. It was a bit scary getting used to not having ANY engine braking, but you could toggle in and out of overdrive at will with the switch, so once I got used to it, it was the best of both worlds

We could have a similar over running clutch in the iMiEV so it truly freewheels. *IF* we didn't need to reverse by reversing the motor - With such a clutch, there would be no reverse unless you had a separate reverse gear. I guess the way they went is the simplest . . . . but a true freewheel would be great for serious hypermilers, wouldn't it?

Don

 

[JoeS]

MLucas, I think your question has been answered: regeneration only occurs if you wish to decelerate. What's great about the iMiEV is that we can control this using -
1) D-Eco-B for three different levels of regen
2) Our foot on the Go-Pedal for precise control over regen
3) The brake pedal to further modulate regen up to its max

We can happily intermix these to provide any level of regeneration we wish. To me, the most cumbersome of the three is using the brake pedal and if I had my 'druthers I would also have a paddle or lever or joystick by the steering wheel allowing me to pull back and give me full manual control over regen (I have that on my modified Insight). Hey, nevertheless, our iMiEV is far superior to the Leaf or Ford FE in this regen capability. Those of you who like driving in B would love a Tesla (either the roadster or S) - its regen is superb, but only controllable primarily with the go-pedal. The Mini-E and the BMW Active-E do that as well.

Don, my impression is that the freewheeling iMiEV motor and its drivetrain exhibits almost no drag - kicking the lever into N really does allow it to coast very freely. I start off from home on a gentle two-mile downslope with fairly low speeds (~35mph=56km/h) and both the Insight in Neutral and the iMiEV in N behave the same way. Just note how easily you can push the iMiEV by hand when it's on the level. Like I keep saying, it's far easier to just pop the iMiEV into N than to try keeping the red power needle halfway between blue and green, although note that the iMiEV manual cautions us not to do that. :roll:

 

[fjpod]

just remember...with the exception perhaps of going down long hills, acquiring regen indicates you used too much acceleration in the first place for the situation you are in.

Of course, we have to keep up with traffic, avoid obstacles, etc...all this cuts into efficiency.

A high mpg driver will take all this into account and pre-plan how his foot should act.

The best place to keep the eco needle is right between charge and eco...i.e at zero...while the car is moving, of course.